An isolated anterior echo-free space is generally regarded as a false-positive echocardiographic finding for pericardial effusion. Even when an anterior echo-free space is accompanied by a posterior echo-free space, the echo-free spaces have been occasionally reported to be falsely positive for pericardial effusion, principally in patients with cardiac neoplasms. The basis for these findings has never been adequately explained. In the present study, evaluation by computed tomographic imaging or necropsy examination of 5 patients in whom there was either an anterior or posterior echo-free space or both demonstrated that subepicardial adipose tissue is the echocardiographic imitator of pericardial effusion.